U.S. patent number 10,680,710 [Application Number 16/256,393] was granted by the patent office on 2020-06-09 for reacquiring communication link based on historical data.
This patent grant is currently assigned to X Development LLC. The grantee listed for this patent is X Development LLC. Invention is credited to Paul Csonka, Baris Ibrahim Erkmen, Travis Lantz.
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United States Patent |
10,680,710 |
Lantz , et al. |
June 9, 2020 |
Reacquiring communication link based on historical data
Abstract
The disclosure provides for a method for reacquiring a
communication link between a first communication device and a
second communication device. The method includes using one or more
processors of the first communication device to receive historical
data related to the first communication device and an environment
surrounding the first communication device. The one or more
processors are then used to determine one or more trends in the
historical data related to fading of the communication link. Based
on the one or more trends, the one or more processors are used to
determine a starting time and an initial search direction for a
search for the communication link. The one or more processors then
execute the search at the starting time from the initial search
direction.
Inventors: |
Lantz; Travis (Dublin, CA),
Csonka; Paul (Redwood City, CA), Erkmen; Baris Ibrahim
(Sunnyvale, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
X Development LLC |
Mountain View |
CA |
US |
|
|
Assignee: |
X Development LLC (Mountain
View, CA)
|
Family
ID: |
70973024 |
Appl.
No.: |
16/256,393 |
Filed: |
January 24, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B
10/1143 (20130101); H04B 10/079 (20130101); H04B
10/1149 (20130101); H04B 10/0779 (20130101); H04W
16/28 (20130101) |
Current International
Class: |
H04B
10/00 (20130101); H04W 16/28 (20090101); H04B
10/077 (20130101); H04B 10/079 (20130101); H04B
10/114 (20130101) |
Field of
Search: |
;398/118,119,127,128,129,130,131,135,136,158,159,121,122,115 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Bai, Shuai , et al., "Predictive filtering-based fast reacquisition
approach for space-borne acquisition, tracking, and pointing
systems", Key Lab of Space Active Opto-Electronic Technology and
Systems, Shanghai Inst. of Technical Physics, Chinese Academy of
Sciences, Shanghai, China, published Oct. 20, 2014, vol. 22, No.
22, pp. 1-14. cited by applicant .
Bertin, Clement, et al., "Prediction of optical communication link
availability: real-time observation of cloud patterns using a
ground-based thermal infrared camera", Optics in Atmospheric
Propagation and Adaptive Systems XVIII, vol. 9641; downloaded from
https://www.spiedigitallibrary.org/conference-proceedings-of-spie
on Dec. 6, 2018, pp. 1-8. cited by applicant .
Saw, Wee-Leong , et al., "Free Space Optical Alignment System Using
GPS", School of Electrical and Computer Engineering, University of
Oklahoma--Tulsa; Proc. SPIE 5712, Free-Space Laser Communication
Technologies XVII, (Apr. 18, 2005), pp. 101-109. cited by
applicant.
|
Primary Examiner: Phan; Hanh
Attorney, Agent or Firm: Botos Churchill IP Law
Claims
The invention claimed is:
1. A method for reacquiring a communication link between a first
communication device and a second communication device, the method
comprising: receiving, by one or more processors of the first
communication device, historical data related to the first
communication device and an environment surrounding the first
communication device; determining, by the one or more processors,
one or more trends in the historical data related to fading of the
communication link; determining, by the one or more processors
based on the one or more trends, a predicted location of the second
communication device; determining, by the one or more processors
based on the one or more trends, a starting time and an initial
search direction for a search for the communication link, wherein
the initial search direction is determined based on the predicted
location of the second communication device; and executing, by the
one or more processors, the search at the starting time from the
initial search direction.
2. The method of claim 1, wherein the determining the one or more
trends includes determining a given trend by: identifying a given
time period during a given cycle where fades occur more often than
in other time periods; and determining a characteristic of
environmental data or physical data from the historical data that
corresponds with the given time period.
3. The method of claim 1, wherein the determining the one or more
trends includes determining a given trend by identifying
characteristics of environmental data or physical data from the
historical data that occurs prior to a fade.
4. The method of claim 1, wherein the determining the one or more
trends includes determining a given trend by: identifying a
characteristic of a fade using physical data from the historical
data; and matching the characteristic of the fade with a
characteristic of environmental data from the historical data.
5. The method of claim 1, wherein the determining the one or more
trends includes determining a given trend by identifying an amount
of drift of the communication device from the linked pointing
direction using physical data from the historical data.
6. The method of claim 1, wherein the determining the starting time
and the initial search direction includes: determining a point in
time when environmental data from the historical data does not
include factors that prevent transmission of a signal from the
first communication device.
7. The method of claim 1, further comprising adjusting, by the one
or more processors, a pointing direction of the first communication
device while executing the search according to current data related
to the first communication device and the environment surrounding
the first communication device.
8. A communication system comprising: one or more sensors
configured to detect data related to the communication system and
an environment surrounding the communication system; a steering
mechanism; and one or more processors operatively coupled to the
one or more sensors and the steering mechanism, the one or more
processors being configured to: receive historical data related to
the communication system and the environment surrounding the
communication system; determine one or more trends in the
historical data related to fading of a communication link with a
remote communication system; determine, based on the one or more
trends, a predicted location of the second communication device;
determine, based on the one or more trends, a starting time and an
initial search direction for a search for the communication link,
wherein the initial search direction is determined based on the
predicted location of the second communication device; and control
the steering mechanism to execute the search at the starting time
from the initial search direction.
9. The system of claim 8, wherein the one or more processors are
configured to determine the one or more trends according to: an
identification of a given time period during a given cycle where
fades occur more often than in other time periods; and a
determination of a characteristic of environmental data or physical
data from the historical data that corresponds with the given time
period.
10. The system of claim 8, wherein the one or more processors are
configured to determine the one or more trends according to a
determination of a given trend by identifying characteristics of
environmental data or physical data from the historical data that
occurs prior to a fade.
11. The system of claim 8, wherein the one or more processors are
configured to determine the one or more trends according to: an
identification of a characteristic of a fade using physical data
from the historical data; and a match of the characteristic of the
fade with a characteristic of environmental data from the
historical data.
12. The system of claim 8, wherein the one or more processors are
configured to determine the one or more trends according to
identification of an amount of drift of the communication system
from the linked pointing direction using physical data from the
historical data.
13. The system of claim 8, wherein the one or more processors are
configured to determine the starting time and the initial search
direction according to: a determination of a point in time when
environmental data from the historical data does not include
factors that prevent transmission of a signal from the first
communication device.
14. The system of claim 8, wherein the one or more processors are
further configured to control the steering mechanism to adjust a
pointing direction of the communication system while executing the
search according to current data related to the communication
system and the environment surrounding the communication
system.
15. A non-transitory, tangible computer-readable storage medium on
which computer readable instructions of a program are stored, the
instructions, when executed by one or more processors of a first
communication device, cause the one or more processors to perform a
method, the method comprising: receiving historical data related to
the first communication device and an environment surrounding the
first communication device; determining one or more trends in the
historical data related to fading of a communication link with a
second communication device; determining, based on the one or more
trends, a predicted location of the second communication device,
determining, based on the one or more trends, a starting time and
an initial search direction for a search for the communication
link, wherein the initial search direction is determined based on
the predicted location of the second communication device; and
executing the search at the starting time from the initial search
direction.
16. The medium of claim 15, wherein the determining the one or more
trends includes determining a given trend by: identifying a given
time period during a given cycle where fades occur more often than
in other time periods; and determining a characteristic of
environmental data or physical data from the historical data that
corresponds with the given time period.
17. The medium of claim 15, wherein the determining the one or more
trends includes determining a given trend by identifying
characteristics of environmental data or physical data from the
historical data that occurs prior to a fade.
18. The medium of claim 15, wherein the determining the one or more
trends includes determining a given trend by: identifying a
characteristic of a fade using physical data from the historical
data; and matching the characteristic of the fade with a
characteristic of environmental data from the historical data.
19. The medium of claim 15, wherein the determining the one or more
trends includes determining a given trend by identifying an amount
of drift of the communication device from the linked pointing
direction using physical data from the historical data.
20. The medium of claim 15, wherein the method further comprises
adjusting a pointing direction of the first communication device
while executing the search according to current data related to the
first communication device and the environment surrounding the
first communication device.
Description
BACKGROUND
Communication terminals may transmit and receive optical signals
through free space optical communication (FSOC) links. In order to
accomplish this, such terminals generally use acquisition and
tracking systems to establish the optical link by pointing optical
beams towards one another. For instance, a transmitting terminal
may use a beacon laser to illuminate a receiving terminal, while
the receiving terminal may use a position sensor to locate the
transmitting terminal and to monitor the beacon laser. Steering
mechanisms may maneuver the terminals to point toward each other
and to track the pointing once acquisition is established. A high
degree of pointing accuracy may be required to ensure that the
optical signal will be correctly received.
The mechanisms of communication terminals may vary physically due
to differences in operation over time. For example, mechanisms may
be cycled through large temperature ranges and experience
significantly varying plant (mechanism) characteristics. Mechanisms
may wear with use, which may change friction and viscosity
characteristics. Mechanisms may also have components that reduce
performance using traditional controls techniques. In these
situations, it may be difficult to compensate for the variability
caused by the changes in the components in order to obtain reliable
operation of a communication terminal.
BRIEF SUMMARY
Aspects of the disclosure provide for a method for reacquiring a
communication link between a first communication device and a
second communication device. The method includes receiving, by one
or more processors of the first communication device, historical
data related to the first communication device and an environment
surrounding the first communication device; determining, by the one
or more processors, one or more trends in the historical data
related to fading of the communication link; determining, by the
one or more processors based on the one or more trends, a starting
time and an initial search direction for a search for the
communication link; and executing, by the one or more processors,
the search at the starting time from the initial search
direction.
In one example, determining the one or more trends includes
determining a given trend by identifying a given time period during
a given cycle where fades occur more often than in other time
periods, and determining a characteristic of environmental data or
physical data from the historical data that corresponds with the
given time period. In another example, determining the one or more
trends includes determining a given trend by identifying
characteristics of environmental data or physical data from the
historical data that occurs prior to a fade. In a further example,
determining the one or more trends includes determining a given
trend by identifying a characteristic of a fade using physical data
from the historical data, and matching the characteristic of the
fade with a characteristic of environmental data from the
historical data.
In yet another example, determining the one or more trends includes
determining a given trend by identifying an amount of drift of the
communication device from the linked pointing direction using
physical data from the historical data. In a still further example,
determining the starting time and the initial search direction
includes determining a point in time when environmental data from
the historical data does not includes factors that prevent
transmission of a signal from the first communication device, or
determining a predicted location of the second communication device
based on the one or more trends. In another example, the method
also includes adjusting, by the one or more processors, a pointing
direction of the first communication device while executing the
search according to current data related to the first communication
device and the environment surrounding the first communication
device.
Other aspects of the disclosure provide for a communication system.
The communication system includes one or more sensors configured to
detect data related to the communication system and an environment
surrounding the communication system; a steering mechanism; and one
or more processors operatively coupled to the one or more sensors
and the steering mechanism. The one or more processors are
configured to receive historical data related to the communication
system and the environment surrounding the communication system;
determine one or more trends in the historical data related to
fading of a communication link with a remote communication system;
determine, based on the one or more trends, a starting time and an
initial search direction for a search for the communication link;
and control the steering mechanism to execute the search at the
starting time from the initial search direction.
In one example, the one or more processors are configured to
determine the one or more trends according to an identification of
a given time period during a given cycle where fades occur more
often than in other time periods, and a determination of a
characteristic of environmental data or physical data from the
historical data that corresponds with the given time period. In
another example, determining the one or more trends according to a
determination of a given trend by identifying characteristics of
environmental data or physical data from the historical data that
occurs prior to a fade. In a further example, the one or more
processors are configured to determine the one or more trends
according to an identification of a characteristic of a fade using
physical data from the historical data, and a match of the
characteristic of the fade with a characteristic of environmental
data from the historical data.
In yet another example, the one or more processors are configured
to determine the one or more trends according to identification of
an amount of drift of the communication system from the linked
pointing direction using physical data from the historical data. In
a still further example, the one or more processors are configured
to determine the starting time and the initial search direction
according to a determination of a point in time when environmental
data from the historical data does not includes factors that
prevent transmission of a signal from the first communication
device, or a determination of a predicted location of the second
communication device based on the one or more trends. In another
example, the one or more processors are further configured to
control the steering mechanism to adjust a pointing direction of
the communication system while executing the search according to
current data related to the communication system and the
environment surrounding the communication system.
Further aspects of the disclosure provide for a non-transitory,
tangible computer-readable storage medium on which computer
readable instructions of a program are stored. The instructions,
when executed by one or more processors of a first communication
device, cause the one or more processors to perform a method. The
method includes receiving historical data related to the first
communication device and an environment surrounding the first
communication device; determining one or more trends in the
historical data related to fading of a communication link with a
second communication device; determining, based on the one or more
trends, a starting time and an initial search direction for a
search for the communication link; and executing the search at the
starting time from the initial search direction.
In one example, determining the one or more trends includes
determining a given trend by identifying a given time period during
a given cycle where fades occur more often than in other time
periods, and determining a characteristic of environmental data or
physical data from the historical data that corresponds with the
given time period. In another example, determining the one or more
trends includes determining a given trend by identifying
characteristics of environmental data or physical data from the
historical data that occurs prior to a fade. In a further example,
determining the one or more trends includes determining a given
trend by identifying a characteristic of a fade using physical data
from the historical data, and matching the characteristic of the
fade with a characteristic of environmental data from the
historical data.
In yet another example, determining the one or more trends includes
determining a given trend by identifying an amount of drift of the
communication device from the linked pointing direction using
physical data from the historical data. In a still further example,
the method also includes adjusting a pointing direction of the
first communication device while executing the search according to
current data related to the first communication device and the
environment surrounding the first communication device.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram 100 of a first communication device and a
second communication device in accordance with aspects of the
disclosure.
FIG. 2 is a pictorial diagram of a network 200 in accordance with
aspects of the disclosure.
FIG. 3 is a flow diagram 300 depicting a method in accordance with
aspects of the disclosure.
DETAILED DESCRIPTION
Overview
The technology relates to a method of acquiring a communication
link using historical data related to a communication device and an
environment surrounding the communication device. The communication
device may be configured to initially acquire the communication
link, or reacquire the communication link after the communication
link goes down, by performing a search through a series of varying
pointing directions.
These features, described in more detail below, can provide a
communication device that may respond to fades and other conditions
quickly. The system may start the search at a particular time from
a more useful starting location and therefore be able to reduce the
time to realign and reestablish the link. The system may also have
a higher average throughput due to reduced search-related downtime
leading to increased availability. In addition, the system may also
use less power and have a longer lifetime as a result of more
efficient searching.
Example Systems
FIG. 1 is a block diagram 100 of a first communication device 102
of a first communication terminal configured to form one or more
links with a second communication device 122 of a second
communication terminal, for instance as part of a system such as a
free-space optical communication (FSOC) system. For example, the
first communication device 102 includes one or more processors 104,
a memory 106, a transmitter 112, a receiver 114, a steering
mechanism 116, and one or more sensors 118.
The one or more processors 104 may be any conventional processors,
such as commercially available CPUs. Alternatively, the one or more
processors may be a dedicated device such as an application
specific integrated circuit (ASIC) or other hardware-based
processor, such as a field programmable gate array (FPGA). Although
FIG. 1 functionally illustrates the one or more processors 104 and
memory 106 as being within the same block, the one or more
processors 104 and memory 106 may actually comprise multiple
processors and memories that may or may not be stored within the
same physical housing. Accordingly, references to a processor or
computer will be understood to include references to a collection
of processors or computers or memories that may or may not operate
in parallel.
Memory 106 may store information accessible by the one or more
processors 104, including data 108, and instructions 110, that may
be executed by the one or more processors 104. The memory may be of
any type capable of storing information accessible by the
processor, including a computer-readable medium such as a
hard-drive, memory card, ROM, RAM, DVD or other optical disks, as
well as other write-capable and read-only memories. The system and
method may include different combinations of the foregoing, whereby
different portions of the data 108 and instructions 110 are stored
on different types of media. In the memory of each communication
device, such as memory 106, calibration information may be stored,
such as one or more offsets determined for tracking a signal.
Data 108 may be retrieved, stored or modified by the one or more
processors 104 in accordance with the instructions 110. For
instance, although the technology is not limited by any particular
data structure, the data 108 may be stored in computer registers,
in a relational database as a table having a plurality of different
fields and records, XML documents or flat files.
The instructions 110 may be any set of instructions to be executed
directly (such as machine code) or indirectly (such as scripts) by
the one or more processors 104. For example, the instructions 110
may be stored as computer code on the computer-readable medium. In
that regard, the terms "instructions" and "programs" may be used
interchangeably herein. The instructions 110 may be stored in
object code format for direct processing by the one or more
processors 104, or in any other computer language including scripts
or collections of independent source code modules that are
interpreted on demand or compiled in advance. Functions, methods
and routines of the instructions 110 are explained in more detail
below.
The one or more processors 104 are in communication with the
transmitter 112 and the receiver 114. Transmitter 112 and receiver
114 may be part of a transceiver arrangement in the first
communication device 102. The one or more processors 104 may
therefore be configured to transmit, via the transmitter 112, data
in a signal, and also may be configured to receive, via the
receiver 114, communications and data in a signal. The received
signal may be processed by the one or more processors 104 to
extract the communications and data.
The transmitter 112 may be configured to output a beacon beam 20
that allows one communication device to locate another, as well as
a communication signal over a communication link 22. The
communication signal may be a signal configured to travel through
free space, such as, for example, a radio-frequency signal or
optical signal. In some cases, the transmitter includes a separate
beacon transmitter configured to transmit the beacon beam and one
or more communication link transmitters configured to transmit the
optical communication beam. Alternatively, the transmitter 112 may
include one transmitter configured to output both the beacon beam
and the communication signal. The beacon beam 20 may illuminate a
larger solid angle in space than the optical communication beam
used in the communication link 22, allowing a communication device
that receives the beacon beam to better locate the beacon beam. For
example, the beacon beam carrying a beacon signal may cover an
angular area on the order of a square milliradian, and the optical
communication beam carrying a communication signal may cover an
angular area on the order of a hundredth of a square
milliradian.
As shown in FIG. 1, the transmitter 112 of the first communication
device 102 is configured to output a beacon beam 20a to establish a
communication link 22a with the second communication device 122,
which receives the beacon beam 20a. The first communication device
102 may align the beacon beam 20a co-linearly with the optical
communication beam (not shown) that has a narrower solid angle than
the beacon beam 20a and carries a communication signal 24. As such,
when the second communication device 122 receives the beacon beam
20a, the second communication device 122 may establish a
line-of-sight link with the first communication device 102 or
otherwise align with the first communication device. As a result,
the communication link 22a that allows for the transmission of the
optical communication beam (not shown) from the first communication
device 102 to the second communication device 122 may be
established.
The receiver 114 may include an optical fiber and a tracking system
configured to detect the optical beam. The tracking system may
include at least a tracking sensor. In addition, the tracking
system may also include a lens, mirror, or other system configured
to divert a portion of a received optical beam to the tracking
sensor and allow the remaining portion of the received optical beam
to couple with the optical fiber. The tracking sensor may include,
but is not limited to, a position sensitive detector (PSD), a
charge-coupled device (CCD) camera, a focal plane array, a
photodetector, a quad-cell detector array, or a CMOS sensor. The
tracking sensor is configured to detect a signal location at the
tracking sensor and convert the received optical beam into an
electric signal using the photoelectric effect. The tracking system
is able to track the received optical beam, which may be used to
direct the steering mechanism 116 to counteract disturbances due to
scintillation and/or platform motion.
Furthermore, the one or more processors 104 are in communication
with the steering mechanism 116 for adjusting the pointing
direction of the transmitter 112, receiver 114, and/or optical
beam. The steering mechanism 116 may include one or more mirrors
that steer an optical signal through the fixed lenses and/or a
gimbal configured to move the transmitter 112 and/or the receiver
114 with respect to the communication device. In particular, the
steering mechanism 116 may be a MEMS 2-axis mirror, 2-axis voice
coil mirror, or piezo electronic 2-axis mirror. The steering
mechanism 116 may be configured to steer the transmitter, receiver,
and/or optical beam in at least two degrees of freedom, such as,
for example, yaw and pitch. The adjustments to the pointing
direction may be made to acquire a communication link, such as
communication link 22, between the first communication device 102
and the second communication device 122. To perform a search for a
communication link, the one or more processors 104 may be
configured use the steering mechanism 116 to point the transmitter
112 and/or the receiver 114 in a series of varying directions until
a communication link is acquired. In addition, the adjustments may
optimize transmission of light from the transmitter 112 and/or
reception of light at the receiver 114.
The one or more processors 104 are also in communication with the
one or more sensors (or estimators) 118. The one or more sensors
118 may be configured to monitor a state of the first communication
device 102. The one or more sensors may include an inertial
measurement unit (IMU), encoders, accelerometers, and/or gyroscopes
configured to measure one or more of pose, angle, velocity,
torques, as well as other forces. In addition, the one or more
sensors 118 may include components configured to measure one or
more environmental conditions such as, for example, temperature,
wind, radiation, precipitation, humidity, etc. In this regard, the
one or more sensors 118 may include thermometers, barometers and/or
hygrometers, etc. While the one or more sensors 118 are depicted in
FIG. 1 as being in the same block as the other components of the
first communication device 102, in some implementations, some or
all of the one or more sensors may be separate and/or physically
remote from the first communication device 102.
The second communication device 122 includes one or more processors
124, a memory 126, a transmitter 132, a receiver 134, a steering
mechanism 136, and one or more sensors 138. The one or more
processors 124 may be similar to the one or more processors 104
described above. Memory 126 may store information accessible by the
one or more processors 124, including data 128 and instructions 130
that may be executed by processor 124. Memory 126, data 128, and
instructions 130 may be configured similarly to memory 106, data
108, and instructions 110 described above. In addition, the
transmitter 132, the receiver 134, and the steering mechanism 136
of the second communication device 122 may be similar to the
transmitter 112, the receiver 114, and the steering mechanism 116
described above.
Like the transmitter 112, transmitter 132 may be configured to
output both an optical communication beam and a beacon beam. For
example, transmitter 132 of the second communication device 122 may
output a beacon beam 20b to establish a communication link 22b with
the first communication device 102, which receives the beacon beam
20b. The second communication device 122 may align the beacon beam
20b co-linearly with the optical communication beam (not shown)
that has a narrower solid angle than the beacon beam and carries
another communication signal. As such, when the first communication
device 102 receives the beacon beam 20a, the first communication
device 102 may establish a line-of-sight with the second
communication device 122 or otherwise align with the second
communication device. As a result, the communication link 22b, that
allows for the transmission of the optical communication beam (not
shown) from the second communication device 122 to the first
communication device 102, may be established.
Like the receiver 114, the receiver 134 includes an optical fiber
and a tracking system configured to detect the optical beam with
the same or similar features as described above with respect to the
receiver 114. In addition, the tracking system may also include a
lens, mirror, or other system configured to divert a portion of a
received optical beam to the tracking sensor and allow the
remaining portion of the received optical beam to couple with the
optical fiber. The tracking system of receiver 134 is configured to
track the received optical beam, which may be used to direct the
steering mechanism 136 to counteract disturbances due to
scintillation and/or platform motion.
The one or more processors 124 are in communication with the
steering mechanism 136 for adjusting the pointing direction of the
transmitter 132, receiver 134, and/or optical beam, as described
above with respect to the steering mechanism 116. The adjustments
to the pointing direction may be made to establish acquisition and
connection link, such as communication link 22, between the first
communication device 102 and the second communication device 122.
In addition, the one or more processors 124 are in communication
with the one or more sensors 138 as described above with respect to
the one or more sensors 118. The one or more sensors 138 may be
configured to monitor a state of the second communication device
122 in a same or similar manner that the one or more sensors 118
are configured to monitor the stat eof the first communication
device 102.
As shown in FIG. 1, the communication links 22a and 22b may be
formed between the first communication device 102 and the second
communication device 122 when the transmitters and receivers of the
first and second communication devices are aligned, or in a linked
pointing direction. Using the communication link 22a, the one or
more processors 104 can send communication signals to the second
communication device 122. Using the communication link 22b, the one
or more processors 124 can send communication signals to the first
communication device 102. In some examples, it is sufficient to
establish one communication link 22 between the first and second
communication devices 102, 122, which allows for the bi-directional
transmission of data between the two devices. The communication
links 22 in these examples are FSOC links. In other
implementations, one or more of the communication links 22 may be
radio-frequency communication links or another type of
communication link capable of travelling through free space.
As shown in FIG. 2, a plurality of communication devices, such as
the first communication device 102 and the second communication
device 122, may be configured to form a plurality of communication
links (illustrated as arrows) between a plurality of communication
terminals, thereby forming a network 200. The network 200 may
include client devices 210 and 212, server device 214, and
communication devices 102, 122, 220, 222, and 224. Each of the
client devices 210, 212, server device 214, and communication
devices 220, 222, and 224 may include one or more processors, a
memory, a transmitter, a receiver, and a steering mechanism similar
to those described above. Using the transmitter and the receiver,
each communication device in network 200 may form at least one
communication link with another communication device, as shown by
the arrows. The communication links may be for optical frequencies,
radio frequencies, other frequencies, or a combination of different
frequency bands. In FIG. 2, the communication device 102 is shown
having communication links with client device 210 and communication
devices 122, 220, and 222. The communication device 122 is shown
having communication links with communication devices 102, 220,
222, and 224.
The network 200 as shown in FIG. 2 is illustrative only, and in
some implementations the network 200 may include additional or
different communication terminals. The network 200 may be a
terrestrial network where the plurality of communication devices is
on a plurality of ground communication terminals. In other
implementations, the network 200 may include one or more
high-altitude platforms (HAPs), which may be balloons, blimps or
other dirigibles, airplanes, unmanned aerial vehicles (UAVs),
satellites, or any other form of high altitude platform, or other
types of moveable or stationary communication terminals. In some
implementations, the network 200 may serve as an access network for
client devices such as cellular phones, laptop computers, desktop
computers, wearable devices, or tablet computers. The network 200
also may be connected to a larger network, such as the Internet,
and may be configured to provide a client device with access to
resources stored on or provided through the larger computer
network.
Example Methods
When the communication link 22 between the first communication
device 102 and the second communication device 122 is lost or
fades, the one or more processors 104 may determine settings for a
search for reacquiring the communication link 22 prior to executing
the search as described below and depicted in flow diagram 300 in
FIG. 3. In FIG. 3, flow diagram 300 is shown in accordance with
aspects of the disclosure that may be performed by the one or more
processors 104 of the first communication device 102. While FIG. 3
shows blocks in a particular order, the order may be varied and
multiple operations may be performed simultaneously. Also,
operations may be added or omitted. The one or more processors 124
may also determine settings for a search for reacquiring the
communication link 22 in a same or similar way.
At block 302, the one or more processors 104 of the first
communication device 102 receive historical data related to the
first communication device 102 and the environment surrounding the
first communication device. The historical data may include
environmental data, such as temperature, humidity, wind patterns,
etc., over a time frame. By way of example, the environmental data
may be obtained using the one or more sensors 118, retrieved from a
local memory, or received from a remote database. The time frame
may be, for example, 12 hours, a day, a month, or a year. The
historical data may also include physical data related to a status
of the first communication device 102, such as telemetry
measurements or IMU measurements from the one or more sensors 118.
The telemetry measurements may include data related to a fade of
the optical signal, such as an amount of power or a frequency
received over a time frame from a beacon beam or a communication
beam. The IMU measurements may include an orientation of the first
communication device 102 over time. The time frame for the
telemetry measurements may be, for example, 30 seconds, 10 minutes,
or a 24 hour period. The sampling rate for these measurements may
be 50 kHz, or more or less, which may also be averaged over equal
intervals in order to track the measurements at a lower frequency,
such as 1 Hz.
At block 304, the one or more processors 104 determine one or more
trends in the historical data related to fading of the
communication link 22 between the first communication device 102
and the second communication device 122. The one or more processors
104 may determine a first trend by identifying a time period during
a 24-hour cycle where fades occur more often than other time
periods and determining a characteristic of environmental data or
physical data that corresponds with the same time period. For
example, the first trend in the historical data may be that fades
occur more often at or around sunrise, or between 5 a.m. and 7
a.m., when the relative humidity is the highest or fog is most
often forecasted or detected. The one or more processors 104 may
also determine a second trend by identifying characteristics of
environmental data or physical data that often occurs just prior to
a fade, such as within 10 seconds, 1 minute, 30 minutes, or more or
less before the fade. Characteristics of the environmental data or
physical data may be related to a gust of wind having at least a
minimum speed. The one or more processors 104 may also determine a
third trend by identifying a characteristic of a fade using the
physical data and matching the characteristic of the fade with a
characteristic of environmental data. For example, the third trend
in the historical data may be that the amount of fluctuation from
maximum to minimum received power (i.e., dynamic range) and/or
amount of signal power over time matches the amount of dynamic
range and/or amount of signal power over time due to the presence
of fog or rain. When fog is coming in, the dynamic range will stay
the same or decrease as fog increases, and the amount of signal
power will steadily drop over time. When rain is present, the
dynamic range will increase or vary more erratically over time, and
the amount of average power will vary up and down at a more rapid
rate than in the presence of fog. The one or more processors 104
may determine a fourth trend by identifying an amount of drift of
the first communication device 102 from the linked pointing
direction using the physical data. In this example, the drift may
be detected as 10 degrees downwards towards the ground using the
IMU measurements and the previously known linked pointing
direction.
At block 306, the one or more processors 104 are configured to
determine a starting time and an initial search direction for the
search using the one or more trends in the historical data. The
starting time may be determined to be a point in time when
environmental data does not include factors that prevent
transmission or receipt of a signal from the first communication
device. For example, the point in time may be after environmental
factors that obstruct transmission or receipt of an optical signal
has left the environment of the first communication device 102. For
example, based on the first trend, the one or more processors 104
may determine the starting time to be at least after 7 a.m., when
the relative humidity historically begins to lower during the day.
Based on the third trend, the one or more processors 104 may
determine the starting time to be after the fog around the first
communication device 102 decreases to an acceptable amount.
The initial search direction may be determined based on a predicted
location of the second communication device 122. For example, based
on the first trend and the third trend, the initial search
direction may be determined as a current pointing direction of the
first communication device 102 since the fade was likely due to
environmental factors unrelated to the pointing direction of the
first communication device 102 or the second communication device
122. Based on the third trend, the initial search direction may be
determined to be a number of degrees opposite the direction of the
gust of wind to counteract a possible shift of the first
communication device 102 or the second communication device 122 due
to the gust of wind. Based on the fourth trend, the initial search
direction may be determined to be 10 degrees upwards away from the
ground to counteract the detected drift of the first communication
device 102.
At block 308, the one or more processors 104 are able to execute
the search at the starting time from the initial search direction.
Executing the search may include controlling the steering mechanism
116 of the first communication device 102 to point the transmitter
112 and/or the receiver 114 in a search pattern comprising a
plurality of directions that starts from the initial search
direction. The plurality of directions may increase in distance
from the initial search direction. When the search pattern is
started from the initial search direction that has been determined
as described above, a linked pointing direction may be closer to
the initial search direction than when the initial search direction
is determined in other ways. In addition, when the search is
started at the starting time that has been determined as described
above, the search may be started when conditions for reacquiring
the communication link are better than when the starting time is
determined in other ways. As such, a communication link may be
reacquired earlier in the search.
In some implementations, the one or more processors 104 may further
determine other settings for the search and execute them. The other
settings may include an amount of power, a frequency, or a width of
a signal. Characteristics of the current environment may be
predicted or detected based on the environmental data received by
the one or more processors 104. The one or more processors 104 may
then select these other settings for the search based on whether
the settings increase detectability of an optical signal in the
current environment.
At block 310, the one or more processors 104 are configured to
adjust a pointing direction of the first communication device 102
while executing the search according to the historical data or
current data related to the first communication device 102. The
adjustment may be made by estimating an amount of offset caused by
changes in the environmental data or the physical data. Similar to
the historical data described above, the current data may include
environmental data, such as temperature, humidity, wind patterns,
etc., and physical data, such as telemetry measurements or IMU
measurements. For example, wind data may be collected as current
data and may be used to estimate an amount of offset caused by an
amount of wind. In some implementations, the one or more processors
104 may also predict an amount of offset according to a trend in
the historical data and/or the current data. For example, a trend
in wind data may indicate that, as an amount of wind steadily
increases, a corresponding amount of offset of the first
communication device occurs. The trend may be applied extrapolated
into a future time to predict an amount of offset that may occur.
The one or more processors 104 may then determine an adjusted
pointing direction to counteract the estimated or predicted amount
of offset caused by the amount of wind and control the steering
mechanism 116 using the adjusted pointing direction. Alternatively,
the one or more processors 104 may apply an amount of drive to
counteract the amount of offset caused by the amount of wind.
At block 312, the one or more processors 104 are configured to
control operation of the communication link after the linked
pointing direction is reached.
Unless otherwise stated, the foregoing alternative examples are not
mutually exclusive, but may be implemented in various combinations
to achieve unique advantages. As these and other variations and
combinations of the features discussed above can be utilized
without departing from the subject matter defined by the claims,
the foregoing description of the embodiments should be taken by way
of illustration rather than by way of limitation of the subject
matter defined by the claims. In addition, the provision of the
examples described herein, as well as clauses phrased as "such as,"
"including" and the like, should not be interpreted as limiting the
subject matter of the claims to the specific examples; rather, the
examples are intended to illustrate only one of many possible
embodiments. Further, the same reference numbers in different
drawings can identify the same or similar elements.
* * * * *
References